Engino Discovering STEM力学セット：カム＆クランクおもちゃ、9歳以上向け（8モデル）

My son finally understood how a crankshaft turns circular motion into the up-and-down stroke of an engine piston—the snail cam model made that click instantly. We’ve already rebuilt three of the 8 models, and the pieces stay snug through all his testing.

The crankshaft model actually turns the way a real engine does, which my son thought was the coolest part. Instructions were clear enough that he built all 8 models without needing my help.

My 10-year-old built the crane model first and spent a solid hour just testing how the cam made the arm lift. The instruction booklet breaks each of the 8 builds into clear steps, so he barely needed my help.